The invention relates to a splice between two ends of yarn as required, for example, when, in the continuous processing of a yarn which is being unwound from one yarn spool, the end of the yarn is reached and it becomes necessary for the starting part of the yarn supplied from another yarn spool to be spliced to the end. Such an operation takes place, in particular, when there is a change of warp beams in weaving machines, when the yarn wound onto one warp beam reaches its end and it becomes necessary for the starting part of the corresponding yarn from a new warp beam to be spliced to the aforementioned end, there resulting a multiplicity of such splices across the width of the warp beam.
The conventional method, employed in connection with the above-described applications, of splicing the end of one yarn to the starting part of another yarn consists in the operation of tying, as described, for example, in DE OS 17 10 938. According to this publication, the starting part and end are held by clamping and are then subjected to a tying operation which is performed by a complicated mechanism. A further known method of splicing consists, according to DE OS 32 47 162, in coaxially aligning the yarns with respect to each other with a small distance between them and in holding them in this position using clamping devices, whereupon a bonding agent is introduced in dosed droplet form into the gap between starting part and end of the yarn, with rollers acting on the place of bonding and rotating said place of bonding in order, at the place of bonding, to obtain a diameter equal to the diameter of the overall yarn.
The method of mechanically tying together the starting part and end of the yarns results in a considerable degree of mechanical complexity with corresponding intensity of maintenance. Furthermore, there is a considerable increase in the diameter of the yarn at the place of tying, this making it impossible in many applications for the yarn to be continuously processed, because, in a weaving machine, for example, the yarn has to run through harnesses and the weaving comb. When the weaving comb is operated, it is moved very closely past the yarn at high speed, wherein a place of tying is exposed to quite considerable frictional and tensile stresses, which may result in the yarn tearing at the place of tying. The continuous processing of tied yarns on weaving machines is, therefore, impossible at present. For this reason, when use is made of the presently conventional method of mechanical tying, an attempt is made to employ the maximum possible lengths of yarns on the warp beams in order in this manner to save on the effort of individually tying all the yarns on the warp beam, something which is associated with a considerable expenditure of time. The consequence of this is that small lot sizes, which would be economically advantageous for relatively short lengths of woven goods, are virtually never produced, because this would necessitate correspondingly shorter lengths of yarn on the warp beams. The additionally known method of introducing a droplet of bonding agent into the gap between the starting part and end of a clamped yarn is virtually never used because, particularly in the case of thin yarns, there is a correspondingly small bonding zone which is not capable of withstanding a high tensile stress during the processing of the yarn and which, therefore, has a tendency to tear.
Known from EP 0 989 218 A1 is a further method of splicing an end of yarn to a starting part of yarn according to which the end and the starting part are firmly held in a position in which they overlap over a considerable length and are twisted together in that position. In order to provide this twisted region with the necessary tensile strength and resistance to reverse twisting, a bonding agent is dabbed onto the twisted region. This method, therefore, comprises two successive process steps, it being necessary first of all for the intertwisted yarns to be firmly held in said position until the bonding agent, having been dabbed onto the twisted region, has set. This slows down the process so considerably that it has not been able to establish itself in practice. It must also be taken into consideration in this connection that the twisted yarns have the tendency to twist back, as a consequence of which the splice is from the outset given the tendency automatically to become undone unless the bonding agent joins the two yarns together really firmly.